Back light assembly and liquid crystal display device having the same

ABSTRACT

A backlight assembly of the present invention includes a light guide plate (LGP), a light reflecting member, two lamps. The LGP includes a light incidence face, a light reflecting face and a light exiting face. The light reflecting face reflects a first light toward the light exiting face to transform the first light into a second light. The second light exits from the light exiting face. A width of the light incidence face is a first distance. The light reflecting member covers the light incidence face so as to form a receiving space. The two lamps are disposed in the receiving space. The two lamps are spaced apart from each other by a second distance. A sum of diameters of the two lamps and the second distance is longer than the first distance. According to the present invention, a weight, a volume and a thickness of the LGP is reduced.

TECHNICAL FIELD

The disclosure relates to a back light assembly and a liquid crystaldisplay (LCD) device having the back light assembly, and moreparticularly to a back light assembly having a reduced weight, volumeand thickness and a liquid crystal display device having the back lightassembly.

BACKGROUND ART

A liquid crystal display device regulates the transmissivity of light bycontrolling the liquid crystal so as to display an image. The thicknessof a liquid crystal layer in a liquid crystal display device is a onlyfew μm, so that the liquid crystal display device has a light weight, athin thickness and a small size in comparison with a cathode ray tube(CRT) display device.

The liquid crystal display device includes a liquid crystal displaypanel assembly, a backlight assembly and a chassis.

The liquid crystal display panel assembly uses the liquid crystal so asto display images. Electric fields applied to the liquid crystal by aminute area of the liquid crystal display panel assembly, regulate thetransmissivity of the light, so that each of the minute area of liquidcrystal display panel assembly have different light quantityrespectively. Therefore, the liquid crystal display panel assemblydisplays images.

The backlight assembly supplies light to the liquid crystal displaypanel assembly. The back light assembly includes a light guide plate(LGP). The light guide plate converts a linear light from a light sourceto planar light having uniform luminance. Therefore, the liquid crystaldisplay device displays high quality images. The back light assemblyincludes a receiving container.

The receiving container receives the back light assembly and the liquidcrystal display panel assembly.

The chassis fixes the back light assembly and the liquid crystal displaypanel assembly. The liquid crystal display panel assembly is fragile.Therefore, the chassis protects the liquid crystal display panelassembly.

The performance of the liquid crystal display device having theseelements is determined by the thickness, the weight, the luminance ofthe display and so on. Especially, when the liquid crystal displaydevice is portable, the thickness, the weight and the volume become moreimportant.

In order to reduce the thickness, weight and volume, many attempts, forexample replacing the glass of the liquid crystal panel with the glasshaving low density, adapting the back light assembly having no sheet,etc. have been tried.

The light guide plate contributes much portion of the weight of theliquid crystal display device. However, replacing the material of thelight guide plate may not reduce the weight of the light guide plate.

Further, the thickness of the light guide plate is not easily reduced,due to the arrangement of a lamp.

The thickness of the light guide plate relates to the diameter of thelamp.

A general liquid crystal display device has at least two lamps arrangedparallel on a light exiting face of the light guide plate to enhance theluminance.

Therefore, in order to reduce the thickness of the light guide plate,the diameter of the lamp may be reduced. However, there is a limit toreduce the diameter of the lamp.

If the diameter is reduced below the limit, the luminance becomes lower,so that the lamp is useless.

DISCLOSURE OF THE INVENTION

The present invention provides a back light assembly having reducedweight, volume and thickness.

The present invention also provides a liquid crystal display (LCD)device having reduced weight, volume and thickness.

In one aspect of the invention, a backlight assembly includes a lightguide plate, a light reflecting member, at least two lamps and areceiving container. The light guide plate includes a light incidenceface, a light reflecting face and a light exiting face. The lightreflecting face reflects a first light toward the light exiting face totransform the first light into a second light. The second light exitsfrom the light exiting face. A width of the light incidence face is afirst distance. The light reflecting member covers the light incidenceface so as to form a lamp receiving space. The light reflecting memberand the light incidence face defines the lamp receiving space.

The two lamps are disposed in the lamp receiving space. The two lampsare spaced apart from each other by a second distance. A sum ofdiameters of the two lamps and the second distance is longer than thefirst distance. The receiving container receives the light guide plateand the light reflecting member.

In another aspect of the invention, the liquid crystal display deviceincludes the back light assembly above described, a liquid crystaldisplay panel assembly, and a chassis. The liquid crystal display panelassembly displays an image. The liquid crystal display panel assemblyfaces the light exiting face. The receiving container receives theliquid crystal display panel assembly. A first portion of the chassispresses an edge of the liquid crystal display panel. A second portion ofthe chassis is combined with the receiving container so as to preventthe liquid crystal display panel from being detached from the receivingcontainer.

According to the present invention, the thickness of the back lightassembly of the liquid crystal display device is reduced, and theluminance of the liquid crystal display device may be increased. Inaddition, the weight and volume of the liquid crystal display device isreduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present invention will becomereadily apparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a partial cross-sectional perspective view showing a backlight assembly according to a first exemplary embodiment;

FIG. 2 is a cross-sectional view showing a wedge type light-guide plateaccording to a second exemplary embodiment;

FIG. 3 is a cross-sectional view showing a flat type light-guide plateof FIG. 1;

FIG. 4 is a cross-sectional view showing a flat type light-guide plateaccording to a third exemplary embodiment;

FIG. 5 is a cross-sectional view showing a flat type light-guide plateaccording to a fourth exemplary embodiment;

FIG. 6 is a partial cross-sectional view showing a back light assemblyhaving a light-guide plate having a round shaped light incidence faceaccording to a fifth exemplary embodiment;

FIG. 7 is a partial cross-sectional view showing a back light assemblyhaving a light-guide plate having a V-shaped light incidence faceaccording to a sixth exemplary embodiment;

FIG. 8 is a partial cross-sectional perspective view showing a backlight assembly according to a seventh exemplary embodiment;

FIG. 9 is a partial cross-sectional perspective view showing a backlight assembly according to an eighth exemplary embodiment;

FIG. 10 is a partial cross-sectional perspective view showing a liquidcrystal display device;

FIG. 11 is a schematic view showing a TFT substrate of FIG. 10; and

FIG. 12 is a schematic cross-sectional view showing a color filtersubstrate of FIG. 10.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a partial cross-sectional perspective view showing a backlight assembly according to a first exemplary embodiment.

Referring to FIG. 1, a back light assembly 600 includes a light guideplate, a light reflecting member 200, lamps 300 and a receivingcontainer 400.

The light guide plate may be a wedge type or a flat type light guideplate.

FIG. 2 is a cross-sectional view showing a wedge type light guide plateaccording to a second exemplary embodiment.

Referring to FIG. 2, the wedge type light guide plate 100 has four sidefaces, a light reflecting face 123 and a light exiting face 125. Lightenters into the light guide plate 100 through one of the four sidefaces. Hereinafter, the side face through which the light enters intothe light guide plate 100 is referred to as a light incidence face 110.

The wedge type light guide plate 100 has one light incident face 110. Athickness of a portion of wedge type light guide plate 100 becomesthinner in the opposite direction of the lamps 300.

A width of the light incidence face is a first distance I₁. A lightreflecting member 200 covers the light incident face 110, so that a lampreceiving space for receiving the lamps 300 is formed.

FIG. 3 is a cross-sectional view showing a flat type light guide plateof FIG. 1.

Referring to FIG. 3, a flat type light guide plate 130 has four sidefaces, a light reflecting face 150 and a light exiting face 160. Lightenters into the light guide plate 130 through two parallel side facesthat are called as light incidence faces 136.

The thickness of the light guide plate 130 is uniform, so that thedistance between the light reflecting face 150. The width of the lightexiting face 160 is a first distance I₁.

One of the wedge type light guide plate of FIG. 2 and the flat typelight guide plate of FIG. 3. may be used for the light guide plate.

Referring to FIGS. 1 and 3, a light reflecting member 200 is attached tothe light reflecting face 150 and the light exiting face 160, so thatthe light reflecting member 200 covers the light incidence face 136.

The light reflecting member 200 includes a first reflecting plate 210, asecond reflecting plate 220 and a third reflecting plate 230. The thirdreflecting plate 230 connects the first reflecting plate 210 with thesecond reflecting plate 220. The first reflecting plate 210 is attachedto the light exiting face 160, and the second reflecting plate 220 isattached to the light reflecting face 150.

The first reflecting plate 210, the second reflecting plate 220, thethird reflecting plate 230 and the light incidence face 136 forms a lampreceiving space 240.

The lamp receiving space 240 receives at least two lamps 300. The atleast two lamps 300 are disposed in parallel and spaced apart from eachother.

Referring again to FIG. 1, a first diameter of the first lamp 310 isreferred to as D₁, and a second diameter of the second lamp 320 isreferred to as D₂. The first diameter D₁ of the first lamp 310 may besubstantially equals to the second diameter D₂ of the second lamp 320.However, the first diameter D₁ of the first lamp 310 may be differentfrom the second diameter D₂ of the second lamp 320. A sum of the firstdiameter D₁ of the first lamp 310 and the second diameter D₂ of thesecond lamp 320 is less than the first distance I₁.

The distance between the outer surfaces of the first lamp 310 and thesecond lamp 320 is referred to as I_(G).

The sum of the first diameter D₁ of the first lamp 310, the seconddiameter D₂ of the second lamp 320 and the distance I_(G) is larger thanthe first distance I₁.

When the sum of the first diameter D₁ of the first lamp 310, the seconddiameter D₂ of the second lamp 320 and the distance I_(G) is larger thanthe first distance I₁, the center of the first lamp 310 and the centerof the second lamp 320 does not exist on the same plane which isparallel to the light incidence face 136. In this case, the width of thelamp receiving space is a first width W₁.

FIG. 4 is a cross-sectional view showing a flat type light guide plateaccording to a third exemplary embodiment.

Referring to FIG. 4, the second distance I₂ that is a width of the lightincidence face 136 of FIG. 4 is smaller than the first distance I₁ thatis a width of the light incidence face 136 of FIG. 3. Therefore, thevolume and weight of the third exemplary embodiment are reduced incomparison with the second exemplary embodiment. In this case, thesecond width W₂ of the lamp receiving space of FIG. 4 is increased incomparison with the first width W₁ of the lamp receiving space of FIG. 3so as to receive the lamps of FIG. 4 that have the same diameters asthose of the lamps of FIG. 3.

FIG. 5 is a cross-sectional view showing a flat type light guide plateaccording to a fourth exemplary embodiment.

Referring to FIG. 5, a center of the first lamp 310 and a center of thesecond lamp 320 are disposed on the same plane that is parallel to alight exiting face 160.

A third distance I₃ that is a width of a light guide plate 130 of FIG. 5is reduced in comparison with the second distance I₂ that is the widthof the light guide plate 130 of FIG. 4. The third distance I₃ is almostequal to (but larger than) the diameters of the first lamps 310 and thesecond lamp 320 (D₁, D₂ I₃).

A weight and a volume of the light guide plate 130 of FIG. 5 becomesmaller than those of the light guide plate of FIG. 4. However, a thirdwidth W₃ of the lamp receiving space 240 becomes larger than the secondwidth W₂ of the lamp receiving space 240 of FIG. 4 so as to receive thelamps of FIG. 5 having same diameters as those of the lamps of FIG. 4.

The thinner the light guide plate is, the wider is the width of the lampreceiving space 240.

Hereinafter, back light assemblies including the lamp receiving spaceshaving reduced widths are disclosed.

FIG. 6 is a partial cross-sectional view showing a back light assemblyhaving a light guide plate having a round shaped light incidence faceaccording to a fifth exemplary embodiment. A back light assemblyaccording to a fifth exemplary embodiment has a light guide plate. Alight incidence face 136 of the light guide plate has guide a groove 136b for accepting the second lamp 320 so as to minimize a fourth width W₄of the lamp receiving space. Referring to FIG. 6, the light incidenceface 136 a facing the second lamp 320 has a lamp receiving groove 136 bthat has a concave shape (or curved shape).

The lamp receiving groove 136 b may receive the entire second lamp 320or a portion of the second lamp 320, so that the fourth width W₄ of thelamp receiving space of the light reflecting member 200 is reduced incomparison with the width W₃ of FIG. 5. Therefore, the volume and weightof the back light assembly may be reduced.

When the first lamp 310 and the second lamp 320 are disposed parallelwith the light exiting face 160, a third distance I₃ that is a thicknessof the light guide plate, and a fourth width W₄ of the lamp receivingspace may be minimized.

As a result, when the first lamp 310 and the second lamp 320 aredisposed parallel with the light exiting face 160, a light guide plate130 has a reduced thickness, a reduced volume and a reduced weight, butthat is a width of the lamp receiving space has increased width.However, the groove 136 b may reduce the width. Therefore, the groove136 b reduces the weight and volume of the light guide plate 130.Further, a luminance of the liquid crystal display panel assembly isincreased, because the groove 136 b increases an area of the lightincidence face, and the groove 136 b changes a path of the light towardthe light exiting face 160.

FIG. 7 is a partial cross-sectional view showing a back light assemblyhaving a light guide plate having a V-shaped light incidence faceaccording to a sixth exemplary embodiment.

Referring to FIG. 7, a lamp receiving groove 136 d is formed at a lightincidence face 136 c facing a second lamp 320.

A cross-section of the groove 136 d has a V-shape. The cross-section istaken along a line perpendicular to a longitudinal direction of thelamps.

The groove 136 d may receive the entire second lamp 320 or a portion ofthe second lamp 320, so that the fifth width W₅ of the lamp receivingspace is reduced.

Therefore, a total length of the back light assembly is reduced evenwhen the light guide plate 130 has thickness 13 almost the same asdiameter D₂ of the second lamp 320.

According to the sixth exemplary embodiment of the present invention,the groove 136 d of the FIG. 7 reduces the width W₅ of the lampreceiving space. Therefore, the weight, the volume and the thickness ofthe back light assembly are reduced. Further, a luminance of the liquidcrystal display panel assembly is increased, because the groove 136 dincreases an area of the light incidence face, and the groove 136 dchanges a path of the light toward the light exiting face 160.

FIG. 8 is a partial cross-sectional perspective view showing a backlight assembly according to a seventh exemplary embodiment, and FIG. 9is a partial cross sectional perspective view showing a back lightassembly according to an eighth exemplary embodiment Referring to FIG.8, a light reflecting member 200 includes a chamfer 250 for enhancingthe light utilization efficiency.

The position of the chamfer 250 is determined according to the positionof the first lamp 310 and the second lamp 320 disposed in the lightreflecting member 200.

The chamfer 250 is formed at a second edge of a light reflecting body200. The second edge is diagonally opposite to a first edge 170 of alight incidence face 136 and a light reflecting face 150. In otherworld, as shown in FIG. 8, the chamfer 250 is formed at the portionwhere a first reflecting plate 210 is connected to a third reflectingplate 230.

The chamfer 250 effectively reflects the light generated from a firstlamp 310 toward the light incidence surface 136.

On the contrary, in FIG. 9, The chamfer 260 is formed at a fourth edgeof a light reflecting body 200. The fourth edge is diagonally oppositeto a third edge of the light incidence face 136 and the light exitingface 160. In other world, the chamfer 260 is formed at the portion wherea second reflecting plate 220 is connected to a third reflecting plate230.

The chamfer 260 effectively reflects the light generated from the firstlamp 310 toward the light incidence surface 136.

The chamfers 250 and 260 reflects the light generated by the first lamp310 effectively toward the light incidence face 136.

The chamfers 250 or 260 of the light reflecting member 200 enhances thelight utilization efficiency.

A receiving container 400 receives the light reflecting body 200, thefirst lamp 310, the second lamp 320 and the light guide plate 130.

FIG. 10 is a partial cross-sectional perspective view showing a liquidcrystal display device.

Referring to FIG. 10, a liquid crystal display device includes a chassis800, a liquid crystal display panel assembly 500, a receiving container400, lamps 300, a light reflecting member 200 and a light guide plate130.

The receiving container 400, lamps 300, light reflecting member 200 andlight guide plate 130 may be one of the previous embodiments, so thatdetailed descriptions of the receiving container 400, lamps 300, lightreflecting member 200 and light guide plate 130 are omitted.

The liquid crystal display panel assembly 500 includes a liquid crystaldisplay panel 540, a tape carrier package 550 and a printed circuitboard (PCB) 560.

The liquid crystal display panel 540 includes a thin film transistorsubstrate (TFT substrate) 510, liquid crystal layer 520 and color filtersubstrate 530.

FIG. 11 is a schematic view showing a thin film transistor substrate ofFIG. 10.

Referring to FIG. 11, a thin film transistor 512 formed on the thin filmtransistor substrate 510 of FIG. 10 includes a gate electrode G, drainelectrode D and source electrode S.

A transparent electrode 511 is formed on a glass substrate of the thinfilm transistor substrate 510. The transparent electrode 511 iselectrically connected to the drain electrode of the thin filmtransistor 512. The transparent electrode 511 comprises Indium Tin Oxide(ITO) or Indium Zinc Oxide (IZO).

The gate electrode G is electrically connected to a gate line 513, sothat a gate driving signal is applied to the thin film transistor 512through the gate line 513.

The gate driving signal turns on the thin film transistor 512.

The source electrode S is electrically connected to a data line 514, sothat an image signal is applied to the transparent electrode 511 throughthe data line 514.

FIG. 12 is a schematic cross-sectional view showing a color filtersubstrate of FIG. 10.

Referring to FIG. 12, the color filter substrate 530 includes colorfilters 531, 532 and 533, a common electrode 534 and black matrix 535formed on a glass substrate 536.

The color filters 531, 532 and 533 are formed on a glass substrate 536.The color filters 531, 532 and 533 face the transparent electrode 511 ofFIG. 11. The color filters include a red color filter 531, a green colorfilter 532, and a blue color filter 533.

The red color filter 531 includes a red color pigment or red color dyesfor filtering the red light from the white light.

The green color filter 532 includes a green color pigment or green colordyes for filtering the green light from the white light.

The blue color filter 533 includes a blue color pigment or blue colordyes for filtering the blue light from the white light.

The common electrode 534 is formed on the color filters 531, 532 and533. The common electrode 534 comprises Indium Tin Oxide (ITO) that isconductive and transparent.

The tape carrier package 550 of FIG. 10 is electrically connected to thegate line 513 and the data line 514 of FIG. 11.

The tape carrier package 550 applies the gate driving signal and thedata-driving signal outputted from the printed circuit board 560 to thegate line 513 and the data line 514, respectively.

As shown in FIG. 10, the liquid crystal display panel assembly 500 isfixed to the receiving container 400. The reflecting plate 410 isdisposed between the bottom face of the receiving container 400 and thelight reflecting face 150 of the light guide plate 130. The reflectingplate 410 reflects the light that is leaked from the light reflectingface 150.

Optical sheets 435 may be interposed between the thin film transistorsubstrate 510 and the light exiting face 160 of the light guide plate130.

For example, the optical sheets 435 may include a diffusion sheet 430and a prism sheet 420. The diffusion sheet 430 diffuses the lightexiting from the light exiting face 160, and the prism sheet 420concentrates the diffused light so as to improve the viewing angle ofthe liquid crystal display device.

A chassis 600 fixes the liquid crystal display panel assembly 500 to thereceiving container 400 and protects the liquid crystal display panelassembly 500.

INDUSTRIAL APPLICABILITY

According to the present invention, the thickness of the back lightassembly of the liquid crystal display device is reduced, and theluminance of the liquid crystal display device may be increased. Inaddition, the weight and volume of the liquid crystal display device isreduced.

Although the exemplary embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these exemplary embodiments but various changes andmodifications can be made by one ordinary skilled in the art within thespirit and scope of the present invention as hereinafter claimed.

1. A backlight assembly comprising: a light guide plate including alight incidence face, a light reflecting face and a light exiting face,the light reflecting face reflecting a first light toward the lightexiting face to transform the first light into a second light, thesecond light exiting from the light exiting face, a width of the lightincidence face being a first distance; a light reflecting member forcovering the light incidence face so as to form a lamp receiving space,the lamp receiving space being defined by the light reflecting memberand the light incidence face; at least two lamps disposed in the lampreceiving space, the two lamps being spaced apart from each other by asecond distance, a sum of diameters of the two lamps and the seconddistance being longer than the first distance; and a receiving containerfor receiving the light guide plate and the light reflecting member. 2.The back light assembly of claim 1, wherein the light incidence face hasa groove for receiving a portion of one of the lamps.
 3. The back lightassembly of claim 2, wherein a cross-section of the groove has a curvedshape, the cross-section being taken along a line perpendicular to alongitudinal direction of the lamps.
 4. The back light assembly of claim2, wherein a cross-section of the groove has a V-shape, thecross-section being taken along a line perpendicular to a longitudinaldirection of the lamps.
 5. The back light assembly of claim 1, wherein adiameter of the two lamps are same with each other.
 6. The back lightassembly of claim 1, wherein the lamps includes a first lamp and asecond lamp, the first lamp being disposed near to a first edge of thelight incidence face and the light reflecting face, and the second lampbeing disposed near to a second edge of the light reflecting member, thesecond edge being diagonally opposite to the first edge.
 7. The backlight assembly of claim 6, wherein the light reflecting member includesa chamfer disposed at the second edge, the chamfer enhancing a lightreflection efficiency.
 8. The back light assembly of claim 1, whereinthe lamps includes a first lamp and a second lamp, the first lamp beingdisposed near to a third edge between the light incidence face and thelight exiting face, and a second lamp being disposed near to a fourthedge of the light reflecting member, the fourth edge being diagonallyopposite to the third edge.
 9. The back light assembly of claim 8,wherein the light reflecting member includes a chamber disposed at thefourth edge, the chamfer enhancing a reflection efficiency.
 10. The backlight assembly of claim 1, wherein centers of the lamps are positionedin a same plane that is parallel to the light exiting face.
 11. A liquidcrystal display device comprising: a back light assembly including, i) alight guide plate including a light incidence face, a light reflectingface and a light exiting face, the light reflecting face reflecting afirst light toward the light exiting face to transform the first lightinto a second light, the second light exiting from the light exitingface, a width of the light incidence face being a first distance, ii) alight reflecting member for covering the light incidence face so as toform a lamp receiving space, the lamp receiving space being defined bythe light reflecting member and the light incidence face, iii) at leasttwo lamps disposed in the lamp receiving space, the two lamps beingspaced apart from each other by a second distance, a sum of diameters ofthe two lamps and the second distance being longer than the firstdistance, and iv) a receiving container for receiving the light guideplate and the light reflecting member; a liquid crystal display panelassembly for displaying an image, the liquid crystal display panelassembly facing the light exiting face and being received by thereceiving container; and a chassis, a first portion of the chassispressing an edge of the liquid crystal display panel, a second portionof the chassis being combined with the receiving container so as toprevent the liquid crystal display panel from being detached from thereceiving container.
 12. The liquid crystal display device of claim 11,wherein the light incidence face has a groove for receiving a portion ofone of the lamps.
 13. The liquid crystal display device of claim 12,wherein a cross-section of the groove has a curved shape, thecross-section being taken along a line perpendicular to a longitudinaldirection of the lamps.
 14. The liquid crystal display device of claim12, wherein a cross-section of the groove has V-shape, the cross-sectionbeing taken along a line perpendicular to a longitudinal direction ofthe lamps.
 15. The liquid crystal display device of claim 11, wherein adiameter of the two lamps are same with each other.
 16. The liquidcrystal display device of claim 11, wherein the lamps includes a firstlamp and a second lamp, the first lamp being disposed near to a firstedge between the light incidence face and the light reflecting face, andthe second lamp being disposed near to a second edge of the lightreflecting member, the second edge being diagonally opposite to thefirst edge.
 17. The liquid crystal display device of claim 16, whereinthe light reflecting member includes a chamfer disposed at the secondedge, the chamfer enhancing a light reflection efficiency.
 18. Theliquid crystal display device of claim 11, wherein the lamps includes afirst lamp and a second lamp, the first lamp being disposed near to athird edge between the light incidence face and the light exiting face,and a second lamp being disposed near to a fourth edge of the lightreflecting member, the fourth edge being diagonally opposite to thethird edge.
 19. The liquid crystal display device of claim 18, whereinthe light reflecting member includes a chamber disposed at the fourthedge, the chamfer enhancing a reflection efficiency.
 20. The back lightassembly of claim 11, wherein centers of the lamps are positioned in asame plane that is parallel to the light exiting face.